Means and method for removing foreign particles from lithographic press



Se t. 16, 1969 J. A. DOMOTOR 3,467,003

MEANS AND METHOD FOR REMOVING FOREIGN PARTICLES FROM LITHOGRAPHIC PRESS 2 Sheets-Shee 1 Filed Jan 31, 1967 INVENTOR;

Julius A. Domotor BY 23% mm, Rsaxmw Attorneys Se t. 16, 1969 J. A. DOMOTOR 3,

MEANS AND METHOD FOR REMOVING FOREIGN PARTICLES FROM LITHOGRAPHIC PRESS Filed Jan. 31, 1967 2 Sheets-Sheet 2 INVENTOR. Julius A. Domotor BY I W WWMl-m Attorneys United States Patent O 3,467,008 MEANS AND METHOD FOR REMOVING FOREIGN PARTICLES FROM LITHOGRAPHIC PRESS Julius A. Dornotor, 1520 Sanchez St., San Francisco, Calif. 94131 Filed Jan. 31, 1967, Ser. No. 613,009 Int. Cl. B41f 9/16, 13/24 U.S. Cl. 101142 17 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION Field of the invention This invention relates to the field of printing, particularly printing by utilization of an offset lithographic press. More particularly, this invention relates to means and method for obviating the formation of blemishes on the product printed in such a press.

Description of the prior art Offset lithographic presses are well known and are widely utilized in the printing industry throughout the world. Heretofore, such presses have experienced extreme difficulty in maintaining the product printed thereon free from blemishes which are attributable to small particles of foreign matter which frequently adhere to the plate cylinder of such a press.

Heretofore, the only procedure available to counteract the blemish formation problem was to stop the press and to wipe off manually any particles of foreign matter which had adhered to the plate cylinder. Such a procedure results in substantial lost press time and substantial waste material in the resulting printed product. Additionally, even when the press is stopped and manually cleaned, additional particles of foreign matter subsequently frequently appear on the plate cylinder from unknown sources, or from sources extremely difficult to control, such as the fabric from the dampening rollers utilized in offset lithographic presses in cooperable relationship with the plate cylinder to apply moisture thereto.

The present invention provides a simple solution to the printing blemish problem and may be incorporated into standard lithographic presses with minimum expense and minimum press structural modification. So far as applicant is aware, no prior art exists which discloses an effective solution to this troublesome printing problem which has been bothering the industry for many years.

SUMMARY OF THE INVENTION The present invention relates to modification of a standard offset lithographic press to provide an improved apparatus and printing method which eliminates printing blemishes from the final printed product. To this end, mechanism is provided in conjunction with at least one of the rollers which are normally in rolling contact with the plate cylinder of a lithographic press. The purpose and function of such mechanism is to insure that the surface speed of such roller is different from the surface speed of the plate cylinder itself. As a result of such speed differential, the surfaces of the plate cylinder and the roller wipe over each other and any particles of Patented Sept. 16, 1969 foreign matter (such as lint, paper bits, or dry ink particles) carried by the plate cylinder are removed and transferred onto the roller from which they are transferred to other rollers of the press to preclude reapplication of the removed particles to the plate cylinder.

In the preferred embodiment disclosed herein, the roller which is positively driven at a surface speed different from the speed of the plate cylinder is selected from one of the group of rollers which transfer ink from an ink supply and apply the ink onto the plate cylinder for subsequent application thereby onto the blanket cylinder of the press. The positively driven inking roller preferably is rotated at a surface speed which is a predetermined degree slower than the surface speed at which the plate cylinder is rotated so that the roller drags or wipes over the surface of the plate cylinder to produce the desired particle removing effect. Such particle removal is efiected on a continuous basis without requiring shutting down of the press or slowing down its normal speed of operation.

From the foregoing, it should be understood that objects of this invention include the provision of an improved lithographic press which is capable of producing printed products which are free of printing blemishes; the provision of a method of printing to produce printed products which are free of printing blemishes; the provision in an offset lithographic press of mechanism for positively driving at least one roller which normally is in contact with the plate cylinder of the press at a surface speed different from the surface speed of the plate cylinder; and the provision in a lithographic press of mechanism for positively driving an inking roller at a surface speed which is a predetermined degree less than the surface speed of the plate cylinder to effect a wiping of the cylinder thereby. These and other objects of this invention will become apparent from the following detailed description in which reference is directed to the accompanying drawings.

DESCRIPTION OF THE DRAWING FIG. 1 is an isometric view, largely schematic, showing the primary cylinders and associated water and ink supply roller systems utilized in a conventional offset lithographic press.

FIG. 2 is a side elevational schematic view of the cylinders and the roller system illustrated in FIG. 1 tion will be set out herein.

FIG. 3 is a side elevational View of a lithographic press showing the plate cylinder and associated rollers with which the subject invention is utilized.

FIG. 4 is a sectional view through that portion of the press to which this invention rel-ates, taken generally in the plane of line 44 of FIG. 3, showing details of the mechanism which performs the improved function of this invention.

FIG. 5 is a generally schematic elevational View of the plate cylinder and its associated foreign material removing roller which further illustrates the gear train drive means preferably utilized to positively actuate the roller.

DESCRIPTION OF THE PREFERRED EMBODIMENT Offset lithographic presses are widely utilized in the printing field throughout the world and details of construction of standard presses are well known. The preferred embodiment of this invention is employed in conjunction with only a limited portion of such a press, namely the plate cylinder and fluid supply roller systems utilized in conjunction with such plate cylinder. Therefore, only those details of construction of such a press which are necessary for an understanding of this invention will be set out therein.

However, for a detailed description and explanation of the operation of an offset lithographic press of the type with which this invention is well adapted for use and into which this invention is readily incorporated, reference is directed to the following publications distributed by The Miehle Company, a division of Miehle-Goss- Dexter, Inc. of Chicago, Ill.: Instruction Book for the Operation of the Miehle 25, 29 and 36 Offset Presses," dated April 195 8, and Parts Catalogue for the 25, 29 and 36 One Color Offset Presses-Press Unit and Delivery Section, dated December 1959.

These Miehle publications disclose in complete detail the component parts of a press of the subject type and reference is directed thereto for a complete disclosure of all constructional features of such a press. Reference hereinafter is directed to features of a press as disclosed in such publications.

At the outset, it should be appreciated and understood that with an offset lithographic press of the type described and disclosed in said publications that, when small particles of foreign matter are deposited on the plate cylinder of such press, small blemishes result on the final printed product because of voids produced in the inked surface of the blanket cylinder over which the paper or like stock being printed is passed. Heretofore, with such a press, the only way to counteract such printing blemishes was to stop the press and wipe all offending particles from the plate cylinder manually. However, such procedure'included no provision to preclude other foreign particles from subsequently coming into contact with and adhering to the plate cylinder to cause the blemish problem to reoccur.

Thus, a continuous problem exists with standard presses which heretofore could be corrected only temporarily by periodically stopping the press and cleaning the plate cylinder. Such periodic stopping is obviously wasteful, expensive and bothersome. As a result, it has become a world wide problem in the lithographic industry, and a continuing challenge no matter how neat and clean the press room is maintained, to preclude printing blemishes from occurring. The stop-gap measure of stopping the press to permit cleaning of the plate cylinder is totally unacceptable as an effective solution to the problem.

The present invention comprises means and a method for obviating the formation of such printing blemishes in a standard offset lithographic press in a simple and expeditious manner requiring minimum modification to the standard mechanisms of such press and without requiring press stoppage.

As will be described, in standard offset lithographic presses, rollers of smaller diameter are cormnonly provided in contact with a plate cylinder of large diameter for applying operating fluids, such as ink and dampening water, to the cylinder. Normally such rollers in contact with the plate cylinder are frictionally driven and rotate at the same surface speed as the plate cylinder. The crux of this invention resides in the simple expedient of positively driving at least one of such rollers, preferably an inking roller, at a surface speed which is different from the surface speed of the plate cylinder so that the surfaces of such roller and the plate cylinder wipe against each other. This wiping action, for reasons not fully understood, effects a transfer of any small foreign particles carried by the plate cylinder from the cylinder onto the positively driven roller.

The removed particles are then transferred by the positively driven roller onto other rollers of the fluid supply system, of which such roller forms a part, and are carried back through such system for collection at a point remote from the plate cylinder. All accumulated particles are removed from the collection point in a single operation after a given printing run of the press has been completed, at which time the entire press is normally stopped and fully cleaned to make it ready for a subsequent run. However, as noted previously, there is no need to shut down the press during a given printing run.

In its broader aspects, this invention embodies the positive driving of a roller which is normally in rolling contact with the press plate cylinder at a differential surface speed relative to the cylinder. In its more specific aspects, such roller preferably is driven at a surface speed which is a predetermined degree slower than the surface speed of the plate cylinder so that the surface of the roller drags or wipes across the surface of the plate cylinder, thereby collecting and wiping off all foreign particles, no matter how small, from the plate cylinder. In practical effect, the results obtained with this simple invention are superior, and the finished printed product has been found to be substantially completely free of printing blemishes, certainly to an extent heretofore not obtainable with conventional presses which do not have incorporated therein the mechanism of this invention.

Referring first to FIGS. 1 and 2, that portion of a standard ofiset lithographic press to which this invention pertains will be described, and the relationship of the conventional press mechanisms to the mechanism of this invention will be pointed out. As seen in FIG. 1, and as is well known in the lithographic art, an offset press includes a series of large rotatable cylinders and series of smaller cooperable rollers, all generally designated 1. The cylinders of such a standard printing system include a smooth hard surfaced plate cylinder 2, a resilient surfaced blanket cylinder 3, and a smooth hard surfaced impression cylinder 4.

The sheet of material to be printed, designated by the arrow identified by numeral 6 in FIG. 1, passes over the impression cylinder and between it and the blanket cylinder to emerge therefrom in the direction of arrow 7 in the completed printed condition. As is well known, the metal plate which is mounted on the plate cylinder has certain areas thereof selectively treated to receive ink, via a photo-mechanical process well known, while other areas thereof are not so treated, but are treated to receive moisture. The blanket cylinder is covered by a smooth sheet or blanket of rubber and its purpose is to transfer ink from the treated areas of the plate onto the sheet of material being printed, in known fashion. Such selective treatment of the plate mounted on the cylinder 2 imparts a printed image, determined by the selective inking treatment, to the sheet of material 6 passing between the smooth, hard surfaced impression cylinder and the blanket cylinder.

The necessary printing ink is applied to the blanket cylinder by the plate cylinder 2, which in turn receives ink from an ink supply system, generally designated 8 in FIG. 1, which comprises a series of cooperable rollers. Also provided in conjunction with the plate cylinder 2 is a dampening Water supply system, generally designated 9 in FIG. 1, which comprises a series of cooperable rollers which apply moistening water to the plate cylinder which is transferred thereby to the blanket cylinder for the purpose well known in the lithographic art.

Generally the plate, blanket and impression cylinders are of essentially the same size and are rotated at the same speed relative to each other from a common drive source. As shown schematically in FIG. 1 such drive source comprises a gear wheel 11 which is meshed with a gear 12 mounted on one end of the impression cylinder. Gear 12 in turn is meshed with a gear 13 mounted on one end of the blanket cylinder, which in turn is meshed with a gear 14 mounted on one end of the plate cylinder.

At its opposite end, as also seen in FIG. 1, the plate cylinder has another gear 16 mounted thereon which actuates the respective rollers of the dampening and inking supply systems of the press in 'known fashion. In this connection, referring first to the dampening system 9, it will be seen that an idler gear 17 is interposed between and meshed with gear 16 and a corresponding gear 18 mounted on one end of a water transfer roller 19. Thus transfer roller 19 is positively driven directly by the plate cylinder 2. Idler gear 17, and other idler gears mentioned hereinafter, have been shown in FIG. 1 but have been omitted from the schematic showing of FIG. 2.

Transfer roller 19 in turn is contacted by a pair of water applying rollers 21 and 22 which contact the peripheries of both roller 19 and plate cylinder 2, as best seen in FIG. 2. Thus, water applied to roller 19 from the water source is applied to rollers 21 and 22 and in turn is applied thereby to the surface of plate cylinder 2 for the well known purpose. Transfer roller 19 in turn receives its water supply from a movable supply roller 23 which is selectively and periodically engagea-ble with a water fountain roller 24 rotatable within a water supply trough 26 in known fashion. Thus, dampening water is picked up by the fountain roller 24, periodically applied to supply roller 23, and applied thereby to the transfer roller 19 for subsequent transfer by applicator rollers 21 and 22 to the plate cylinder 2. It should be noted that the applicator rollers 21 and 22 are frictionally driven at the same surface speed as the plate cylinder.

The ink supply system, although somewhat more complex and including more rollers than the dampening system just described, is in broad general respects generally the same as the dampening system. In this regard, the inking system comprises a primary gear driven supply roller 31 (FIG. 1) having a gear 32 mounted on one end thereof which is meshed, through an idler gear 33, with the gear 16 carried by the plate cylinder. Secondary gear driven supply rollers 34 and 36 having gears 37 and 38 mounted thereon are similarly meshed with and driven by gear 16 on plate cylinder 2 by means of idler gears 39 and 41, respectively.

Roller 34, as perhaps best seen in the schematic showing of FIG. 2, has a pair of inking rollers 42 and 43 engaged therewith and normally frictionally driven thereby. Such inking rollers are interposed between the secondary supply roller 34 and plate cylinder 2. Other auxiliary supply rollers 44, 46, and 47 are similarly engaged with the secondary supply roller 34 and with each other for the purpose of insuring effective ink transfer from the ink supply to the surface of the plate cylinder. It will be noted that auxiliary roller 44 also is engaged with the primary gear driven roller 31.

The other secondary supply roller 36 also has a pair of inking rollers 48 and 49 engaged therewith and normally frictionally driven thereby and interposed therebetween and the plate cylinder, as perhaps best seen in FIG. 2. Similarly, a pair of auxiliary supply rollers 51 and 52 are engaged with the secondary supply roller 36 and frictionally driven thereby. Roller 52 in turn is also engaged with the primary gear driven roller 31.

An additional series of auxiliary frictionally driven supply rollers 53, 54, 56, 57, 58 and 59 are operatively interposed between the primary supply roller 31 and a movable supply roller 61, which in turn is selectively and periodically engageable with an ink fountain roller 62 mounted in close proximity for rotation relative to an ink trough '63 in which a supply of ink is maintained.

Thus, in known fashion, upon operation of the press, ink is withrdawn from the trough 63 by roller 62 and is transferred through the series of rollers just described until it is applied to the surface of the plate cylinder by the four spaced inking rollers 42, 43, 48 and 49.

The cylinders and fluid supply roller systems thus far described are conventional and found in standard lithographic presses available on the open market, as described in the aforementioned Miehle publications. It should be specifically noted that in such a standard press none of the inking rollers 42, 43, 48 and 49, or the dampening rollers 21 and 22, which normally are in rolling contact with the plate cylinder, are driven other than frictionally. That is, none of such fluid applying rollers is positively driven via gears or other drive mechanisms.

As a result, each of such rollers travels at a surface speed corresponding generally to the surface speed of the plate cylinder. Heretofore the sole purpose for such inking rollers was to apply a uniform coating of ink to the plate cylinder in known fashion. The dampening rollers perform the same function with dampening water.

However, this invention specifically alters the standard operative relationship of at least one of the fluid applying rollers of the inking or dampening systems relative to the plate cylinder. That is, the means for rotating a preselected one of such rollers is modified so that the surface speed of rotation of such roller is positively maintained different from the speed of rotation of the surface of the plate cylinder. In this connection, it has been found preferable to alter the surface speed of one of the inking rollers. Preferably the first roller in the series of inking rollers closest to the dampening rollers, namely roller 42 as best seen in FIG. 2, has its speed of rotation altered for most effective results. This speed differential is effected in the preferred embodiment by positively driving inking roller 42 from a suitable drive mechanism especially provided therefor. This is in distinction to presses of the prior art in which such inking rollers and other fluid applying rollers are only frictionally driven through roller systems of the type described previously.

The purpose of the positive drive imparted to inking roller 42 is to cause the surfaces of the plate cylinder and the inking roller to wipe or rub against or over each other so that any particles of foreign matter which have become adhered to the plate cylinder will be wiped or rubbed off by the inking roller 42. Inking roller 42 and its associated ink supply rollers normally are formed with a rubber or like resilient covering. As a result, the wiping effect described is produced without damaging the inking rollers or any of the other mechanisms of the press. Also, because of the resilient covering, particles of foreign matter wiped from the plate cylinder by the inking roller 42 are easily transferred back through the chain of roller-to-roller contacts toward the ink supply trough 63. In this connection, it has been found that removed particles of foreign matter are progressively transferred back through the inking supply and accumulate generally in the area of rollers 57, 58 and 59 at the top of the ink supply system from which they may be readily removed in a single operation at the end of a given printing run when the entire press is cleaned.

The exact reasons for the effective removal of particles of foreign matter from the plate cylinder by the simple expedient described are not fully known but tests have established that the expedient disclosed herein is highly effective in accomplishing its intended purpose.

To effect the desired positive drive speed differential between the inking roller 42 and the surface of plate cylinder 2, the simple expedient shown in FIG. 5 has been devised. In this regard, by merely adding a pair of meshed gears in conjunction with secondary ink supply roller 34 and inking roller 42, the results sought may be achieved. As seen in FIG. 5, as noted previously, supply roller 34 is positively driven from gear 16 attached to plate cylinder 2 by means of idler gear 41 which is meshed with gear 38 carried on roller 34. At its other end, roller 34 is provided with another gear 66 in accordance with this invention. A similar gear 67 is also added to and mounted on the end of inking roller 42 and meshed with gear 66.

Thus, by proper gear ratio selection, determined in accordance with the relative diameters of the rollers 34 and 42 and the extent of speed differential desired, inking roller 42 may be rotated at any surface speed, faster or slower as desired, relative to the surface speed of plate cylinder 2. By this uncomplicated expedient of adding two additional gears to a standard offset lithographic press, complete and effective removal of troublesome particles of foreign matter may be insured.

While it is also contemplated within the scope of this invention that improved printing results may be obtained by driving inking roller 42 at a surface speed somewhat faster than the surface speed of the plate cylinder, highly desirable results have been obtained by reducing the surface speed of inking roller 42 relative to the surface speed of the plate cylinder, and the preferred embodiment of this invention incorporates such a speed reduction. In this connection, it has been determined that altering the speed of the inking roller within the range of 3 to 30% less than the preselected speed at which the plate cylinder normally rotates produces satisfactory results. Highly effective results have been obtained when inking roller 42 is operated at a speed reduction within the range of approximately 15 to 20%. Speed differentials in similar effective ranges are contemplated in embodiments which employ faster surface speeds of the inking roller relative to the plate cylinder.

Referring now to FIGS. 3 and 4, a more detailed description of the specific construction of the preferred embodiment of the mechanism of this invention as embodied in a standard press will be described. Such figures also show the related mounting arrangement for the inking rollers and the water dampening rollers used in conjunction with the plate cylinder, and the means for moving such inking and dampening rollers selectively out of contact with the plate cylinder when desired in accordance with known press operating and cleaning practices.

In this latter regard, and referring first to FIG. 3, the means for moving the inking rollers 42, 43, 48 and 49 simultaneously out of contact with the periphery of the plate cylinder 2 comprises a crescent shaped actuating plate 71 including an enlarged boss 72 which is mounted on a pivot shaft 73 which in turn is secured to a rigid side frame member 74 f the press. A similar side frame member 74 is provided at the opposite side of the press, as seen in FIG. 4, on which is mounted another actuating plate 71 and other related structure corresponding to the operating structure described hereinafter with respect to the left side of the press only. That is, identical means is provided at each side of the press for selectively moving the inking rollers, but only one such means will be described.

The actuating plate 71 has secured at its lower end 76 a projecting pin 77 on which is positioned a rotatable member 78. Roller member 78 in turn is engaged with an eccentric boss 79 carried on an enlarged portion 81 of an operating handle 82 which is pivotally mounted on shaft 83 connected to frame member 74 of the press.

Upon pivoting operating handle 82 from the solid line position of FIG. 3 toward the dotted line position shown therein, the eccentric boss 79 will force actuating plate 71 to rotate about the axis of shaft 73 in a counterclockwise direction for the purpose of urging the respective inking rollers 42, 43, 48 and 49 away from the periphery of the plate cylinder. This is accomplished by an upper edge 84 of plate 71 contacting a series of adjustable projections, each designated 86, operatively engaged with the edge of the plate and with the respective rollers, as will be described. Upon return of the operating handle 82 towards the solid line position, the plate 71 permits the inking rollers to again come into contact with the plate cylinder.

As seen in FIG. 3, each of the adjustable projections 86 is mounted on a link member 87 which has its opposite ends formed with arcuate forked yokes. The yoke at the upper end of each link is engaged with an associated inking roller, while the yoke at the lower end is engaged with rigid mounting structure, generally designated 88, which projects from the side frame member 84 and is secured thereto. Details of this arrangement are set out hereinafter with respect to inking roller 42. It should be noted that actuating plate 71 is provided with a series of openings 89 to accommodate structures 88 therethrough.

The means for movably mounting the positively driven inking roller 42 includes mechanism for normally holding such roller in spring urged engagement with the plate cylinder. To this end, inking roller 42 is mounted on an elongated shaft 91 on which the aforementioned gear 67 is secured by means of key 92. Shaft 91 at each of its opposite ends includes a spool member 93 which is supported by a link 94 having opposite forked yoke ends as described previously with respect to links 87 engaged with the other inking rollers. A similar spool 95 is secured by a threaded fastener 96 to frame member 74 and is engaged with the lower end of link 94 for the purpose described previously with respect to links 87. An adjustable key member 97 precludes spool 93 from becoming disengaged with the yoke end of link 94. Key 97 is mounted on a housing 103 described hereinafter.

Shaft 91 in turn is engaged by a non-metallic pressure applying member 98, preferably formed from a plastic having low frictional characteristics, which is urged into contact with shaft 91 by means of a strong coil spring 99, the pressure of which may be adjusted by a set screw 101 in engagement therewith as seen in FIG. 3. Set screw 101 is threadedly engaged in a socket 102 which in turn is threadedly received through a top opening in a generally open housing 103 provided at the upper end of links 94. The position of adjustments of the socket 102 may be threadedly modified selectively but is retained in a preselected position of adjustment by means of a nut 106 threaded on the socket 102 and engaged with the upper surface of the housing 103, as seen in FIG. 4.

Thus, normally the inking roller 42 is maintained by spring pressure in firm contact with the periphery of the plate cylinder, such pressure being selectively adjustable as required for particular operating needs. However, upon actuation of the handle 82 to pivot actuating plate 71, the inking roller 42 may be moved, against the urging of spring 99, away from the periphery of the plate cylinder for adjustment and cleaning purposes, as is well known.

As seen in FIG. 3 also, a similar eccentric operating arrangement, actuated by an operating handle 105, for moving the dampening rollers 21 and 22 out of contact with the periphery of the plate cylinder is provided, as shown in dotted lines. Because such means for moving the dampening rollers forms no part of this invention and is generally similar to the means for moving the inking rollers as described herein, details thereof are not set out herein.

I claim:

1. In a lithographic press, the combination comprising:

(A) a rotatable lithographic plate cylinder,

(B) means for rotating said cylinder in a counterclockwise direction when viewed from one end of said press,

(C) a rotatable roller having a generally smooth nonmetallic resilient surface in direct rolling contact with the surface of said plate cylinder, and

(D) means for positively rotating said roller in a clockwise direction when viewed from said end of said press and at a surface speed which is different from the surface speed of said plate cylinder so that the surfaces of said plate cylinder and said roller wipe over each other and in so doing particles of foreign matter carried by said plate cylinder are removed therefrom and transferred onto said roller without damage to the surface of said plate cylinder.

2. The press combination of claim 1 which further includes:

(E) other means in contact with said roller for receiving said removed particles therefrom and transferring the same away to prevent their reapplication to said plate cylinder.

3. The press combination of claim 1 in which:

(E) said roller comprises an inking roller which transfers ink from a supply thereof and applies same onto said plate cylinder during a printing operation, whereby said roller performs the dual function of inking said plate cylinder while simultaneously removing particles of foreign matter therefrom.

4. In combination in a lithographic press,

(A) a rotatable lithographic plate cylinder,

(B) means for rotating said plate cylinder in a counterclockwise direction when viewed from one end of said press and at a preselected surface speed,

(C) a roller having a generally smooth non-metallic resilent surface in direct rolling contact with said plate cylinder, and

(D) means for positively rotating said roller relative to said plate cylinder in a clockwise direction when viewed from said end of said press and at a surface speed which is different from the surface speed of said plate cylinder so that the surfaces of said plate cylinder and said roller wipe against each other during relative rotation thereof and in so doing effect removal of particles of foreign matter carried by said plate cylinder and transfer thereof to said roller without damage to the surface of said plate cylinder.

5. The combination of claim 4 in which:

(B) said means for rotating said roller includes mechanism for positively driving said roller at a surface speed which is slower than the surface speed of said plate cylinder.

6. The combination of claim 4 in which:

(B) said roller comprises an inking roller Which is a portion of a mechanism which transfers ink from an ink supply onto the surface of said plate cylinder during a printing operation, whereby said roller performs the dual function of inking said plate cylinder while simultaneously removing particles of foreign matter therefrom.

7. The combination of claim 4 in which:

(B) said means for rotating said roller comprises a positive drive gear train mechanism operatively engaged with said roller, said gear train mechanism being selected to insure rotation of said roller at a predetermined differential surface speed relative to the surface speed of said plate cylinder.

8. In an offset lithographic press, the combination comprising:

(A) a series of rotatable cylinders including an impression cylinder, a blanket cylinder, and a lithographic plate cylinder,

(B) means for rotating each of said cylinders at a preselected surface speed, said plate cylinder being rotated in a counterclockwise direction when viewed from one end of said press,

(C) means for applying printing ink to said plate cylinder including a series of rotatable rollers at least some of which are in direct rolling contact with the surface of said plate cylinder, said series of rollers receiving ink from a supply thereof and transferring the same onto said plate cylinder, wherein the improvement comprises,

(D) means for removing particles of foreign matter from the surface of said plate cylinder which may have become adhered thereto during a printing operation without interrupting such printing operation and while ink is being applied to said plate cylinder, comprising:

(1) mechanism for positively rotating one of said rollers which is in rolling contact with said plate cylinder in a clockwise direction when viewed from said end of said press and at a preselected surface speed which is different from the surface speed at which said plate cylinder is rotated so that said roller wipes over said plate cylinder and in so doing removes said particles of foreign matter therefrom without damage to the surface thereof,

(2) said one roller having a generally smooth nonmetallic resilient surface in contact with the surface of said plate cylinder,

(3) said mechanism comprising a positive drive rotatable gear train operatively engaged with said one roller to insure rotation thereof in said clockwise direction and at said preselected surface speed.

9. The press combination of claim 8 in which the other rollers of said series of rollers which are not in rolling contact with said plate cylinder cooperate with said one positively driven roller in transferring said removed particles of foreign matter away from said one positively driven roller to prevent reapplication of such particles to said plate cylinder.

10. The press combination of claim 8 in which the gears of said positive drive gear train have a ratio relative to each other which insures rotation of said one roller at a surface speed which is slower than the surface speed of said plate cylinder.

11. The press combination of claim 10 in which said gears positively drive said roller at a surface speed which is within the range of approximately 3% to 30% slower than the surface speed of said plate cylinder.

12. A method of removing particles of foreign matter from a rotating lithographic plate cylinder of a lithographic press, comprising:

(A) rotating said plate cylinder in a counterclockwise direction when viewed from one end of said press and at a preselected surface speed,

(B) positioning a rotatable roller having a generally smooth non-metallic resilient surface in direct rolling contact with the surface of said plate cylinder, and

(C) positively rotating said roller in a clockwise direction when viewed from said end of said press and at a surface speed which is different from the surface speed of said plate cylinder so that the surfaces of said plate cylinder and said roller wipe over each other and particles of foreign matter carried on said plate cylinder are transferred onto said roller by such wiping without damaging the surface of said plate cylinder.

13. The method of claim 12 in which:

(D) said roller is positively rotated at a preselected surface speed which is slower than the surface speed of said plate cylinder.

14. The method of claim 12 which further includes:

(D) providing means in contact with said roller for receiving and carrying of said removed particles of foreign matter away from said roller to prevent reapplication of such particles to said plate cylinder.

15. The method of claim 13 in which:

(B) said roller is positively driven at a surface speed within the range of approximately 3% to 30% slower than the surface speed of said plate cylinder.

16. The method of claim 13 in which:

(B) said roller is positively driven at a surface speed which is within the range of approximately 15% to 20% slower than the surface speed of said cylinder.

17. A method of removing particles of foreign matter from a lithographic press, which includes a lithographic 11 surface of said plate cylinder for rotating such one roller in a clockwise direction when viewed from said end of said press, and (C) positively rotating said one roller with said means in said clockwise direction and at a surface speed which is different from said preselected surface speed of said plate cylinder, so that the resilient surface of said one roller wipes over the surface of said plate cylinder and particles of foreign matter carried on said cylinder are picked up :by said one roller by such wiping without damaging the surface of said plate cylinder.

References Cited UNITED STATES PATENTS 463,442 11/1891 Dahm 101425 XR 774,822 11/1904 Biette 101425 XR Schmidt 101--350 Schmidt 101349 Harless 101350 Remer 101350 XR Saul 101350 XR Allen 101142 XR Wildeman 101148 Meltz 101348 10 ROBERT E. PULFREY, Primary Examiner C. D.CROWDER, Assistant Examiner US. Cl. X.R. 

